feat(cli): add common note support

[jamesgao-jpg]

What this changes

• Adds shared --note and --note-file options to backend CLI commands.
• Resolves the supplied context centrally into task_config.db_config.note, which is already serialized into each result JSON.
• Ensures Endee's custom CLI runner also resolves note files before constructing its task.
• Rejects conflicting options, empty note files, and non-UTF-8 note files.
• Preserves Pinecone's existing --note behavior through the common implementation.
• Documents how to attach structured or multiline benchmark context.

Compatibility

• Existing CLI commands remain unchanged when neither option is supplied.
• This does not change the result schema because DBConfig.note already exists.
• Backend connection behavior is unchanged: provider clients receive their existing explicit DBConfig.to_dict() connection fields, not the note metadata.

Verification

• make lint
• make unittest — 1 passed
• python -m pytest tests/test_cli_note.py -q — 7 passed
• python -m pytest tests/test_milvus_zilliz_cli.py -q — 2 passed
• Verified --note and --note-file help output for Zilliz Cloud and Pinecone commands.

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: jamesgao-jpg
To complete the pull request process, please assign xuanyang-cn after the PR has been reviewed.
You can assign the PR to them by writing /assign @xuanyang-cn in a comment when ready.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[XuanYang-cn]

resolve_db_note() checks the value truthiness, so an explicitly supplied empty value bypasses the mutual-exclusion check: --note "" --note-file README.md --dry-run succeeds and uses the file. This contradicts the documented mutually-exclusive behavior. Please enforce exclusivity based on whether each Click option was supplied, and add this empty-inline case to the regression test.